Electronic flasher system



0&8, 1959 INVENTOR HELMER T PEDERSON ATTORNEY 2,916,670 ELECTRONIC FLASHER SYSTEM llelmer T. Pederson, Solana Beach, Calif., assign'or to Bill Jack Scientific Instrument Co., Solana Beach, Calif., a corporation of California Application March 15, 1957, Serial No. 646,488 8 Claims. (Cl. 315-209) This invention relates to electronic flasher systems for signal lights for various purposes, but primarily in aircraft lighting and warning systems.

The primary object of this invention. is to provide a flasher system for signal lights in which there are no moving elements, thus assuring more efiicient operation and longer life. 1

A more specific object of this inventionis tov provide a free running static flasher system for signal lights in which the flashing rates are determined solely by. the electrical components of the system.

Another object of this invention is to provide a flasher system for signal lights which is operable over awide range of voltages and in which the flashing rate is in dependent of voltage. a y

A further object of this invention is to provide a flasher system for signal lights in which .the electrical components in the system may be replaced to derive flashing rates of different durations.

Another object of this invention is to ,provide a flasher system for signal lights which requires no maintenance or service time. p

With the foregoing and other objects in view the in- .vention resides in the following specification and appended claims certain embodiments thereof being illust'ratedin the accompanying drawing in which:

Figure 1 is a schematic circuit diagram of the flasher system comprising the invention. 1 I Figure 2 is a schematic circuit diagram of a-modified form of'the invention as illustrated-by Figure 1.

Referring now more particularly toFigure 1, itwill be noted that the flasher system includes a pair of transistor units 1 and 2. Transistor 1 includes a collector 3, an emitter 4 and a base 5. Transistor 2 includes a; collector 6, an emitter 7 and a base 8. Emitters 4- and 7 are connected through resistances 9 and 10 respectively to the positive terminal 11 of a source of DC. potential (not shown) The base 5 of transistor 1 is connected to a parallel circuit including a condenser 12 and a resistance 13 and this R.C. circuit is grounded at 14 through an incandescent lamp 15. The base 8 of transistor 2 is connected to a parallel circuit including a condenser 16 and resistance 17, and this R.C. circuit is grounded at 14 through an incandescent lamp 18.

The collector 6 of transistor 2 is connected to a point 19 in the line 20 between the lamp and the R.C. circuit of transistor 1. The collector 3 of transistor 1 is connected to a point 21 in the line 22 between the lamp 18 and the R.C. circuit of transistor 2.

The operation of the system is determined by the two operating modes of each transistor, namely saturation and cutoff. Since the transistors are in an unstable initial condition, the application of a line voltage at positive terminal 11 will result in the collector, emitter and base drawing current. The base 5 current will charge condenser 12 and this current will be reflected as a voltage drop across lamp 18. The condenser 16 is also being 2 charged during this initial voltage application to terminal 11 from the base 8 of transistor 2.

The voltage drop across lamp 18* and the charge on condenser 16 are additive, and'as the transistor 1 continues to draw current the voltages at base 8 on'transistor 2 will be driven to a cutoif condition with respect to transistor 2. The resistor-17 determines the time forthe charge to leak off condenser 16, and at the moment the base 8 begins to conduct again, the voltage across lamp 15 will begin to increase, building up a combined'voltage with condenser 12 at base 5 to place transistor 1 -in;a cutoif condition. Transistor 2 will then. proceed togsaturation and will remain in this state due to the fact that with transistor 1 in a cutoff condition, the voltage on lamp 18 has been removed, and the current required to recharge. condenser 16, after discharge ,t-hroughresistance 17, will continue to be drawn from thecurrent flow at the base 8. When the charge on condenser 12 has leaked ofl through resistance 13 the base 5 be,- gins to conduct again and the voltage across lamp18 will begin to increase and the cycle will repeat. Thus itvwill be apparent to one skilled in the art that thelampj18 \will be illuminated whentransistor 1 is operating in its saturation'mode, while simultaneously lamp 15 will be dark with transistor 2 operating in its cutoff condition. As the cycle reverses, the illumination of lamps ,15 and 18 reverses. The R-C circuit for transistor 2 will therefore determine the light and dark periods for-lamp 15 while the R-C circuit for transistor 1 will determine the same periods for lamp 18. By varying the resistora'and condenser values connected to. each transistor, the time of the light and dark periods may be altered to .suit various applications.

The resistors 9 and 10 are emitter bias resistors and are utilized to leave suflicient voltage across the collector and the emitter of each transistor when in the cutoff condition to en'able'the transistor to operate as a trigger when its base begins to draw current. The; values of-resistors 9 and 10 are dependent onthe types of transistors used and the minimum voltages these transistors need to conduct. e

It will be'obvious to one skilled in the art that this system is free running in characterand'that the lamps will continue to flash as long as; the system is energized; It willalso be obvious that no moving parts are required to control the flashing of the-lamps and that the system is staticv in character. a

The circuit .of Figure 2 is identical in operation to that of Figure 1. However, the lamp'15 of Figure 1 has been replaced by an equivalent resistance 23 to arrive at a suitable circuit where only one flashing lamp is desired. While other lamps may be utilized, the present invention has been practiced with lamps having an equivalent resistance of 680 ohms.

Thus it should be apparent to one skilled in the art that the flasher system of this invention provides a fully automatic cycling operation to control the light and dark periods of one or more lamps without resorting to any controls involving the use of moving parts.

I claim:

1. A free running static flasher system comprising a pair of transistors, a lamp in circuit with each transistor, means to apply a positive potential to the transistors, control means connected to each transistor to determine the cutoff period of each transistor, and means cross-connecting each transistor to the lamp circuit of the other transistor, each said lamp being energized or de-energized in accord with operating conditions of the transistor to which it is cross-connected.

2. A free running static flasher system comprising a pair of transistors, each including an emitter, a collector and a base, a lamp in circuit with the base of each transistor, and ground, means to the emitterof'each'transistor, control means connected in the lamp circuit to the baseof each transistor between the lamp and the base to determine the cutofl? period of each transistor, and means cross-connecting the collector of each transistor manemp circuit of thepther transistor at a point between thelamp and the control means, 'achsaid lamp-"being energized or de-energiz ed in accord with theoperating condition of the transistor to which it is cross-connected.

33 A free running static flasher systemv comprising a pair of transistors each including an emitter, a collector and a-base, a lamp in circuit with the base of each transistor and ground, circuit means to apply. ajpositive potential to the emitter of eachwransistoni resistance means connected in said e' mitterfpotential circuit topositiv'ely-bias" each transistor, control means connected in the lamp circuit to "thejbase of each transistor between th lamp and the base todeterminethe cutoffperiod 'ot each' transistor, and means cross-connecting the colle 6i of each transistor to the lamp circuit of theothe'r tjrari sistor at-a point between the lamp and the control means, eachsaid lamp being'energized or de-energizedin ac cord with the operating condition of the transistorto which it is cross-connected.

- 4. A free running static flasher system comprising a pair of transistors, a lamp in circuit with each transistor, circuit means to"direct a positive potential to'each of thetransistors, resistance means conneetedin the'potential directing circuit means of each transistor to positively bias -eachtransistor, control means connected to' each transistor to determine the cutoif period of "each transistor, and means cross-connecting each transistor to the lamp circuit of the other transistor, each said lamp being energized or tie-energized in accord with operatingconditions'of'the transistor to which it is cross-connected. 5. "A free running static flasher system comprising a pair of transistors, each including an emitter, a collector and a' base, a lamp in circuit with the base of th e first transistor and ground, a resistor in circuitwith the base of the second transistor 'and ground, means to apply' alpositive potential to the emitter ofeach transistor, controlmeans connected in the lamp circuit to the baseofthe first transistor between the lamp and the base and between the'rcsistor and the base'of the second transistor to determine the cutofi period of each transistor,"mean's cross-connectingthe collector of the second transistorto the lamp circuit of the firsttransistor at a-rpointisbetween' the 'lamp -and the 'controlmea'ns, an'd means-'cross-connectingthe collector of the first transist'or to theresistor circuit of the second transistor ata point between the resistor and thecontrol means, the said damp-being energized or de energized in accord with the operating condition of the second transistor.

to apply apositive potential a .-6. A tnee mnning static flasher system -comprising-a pair of transistors, each including an emitter, a collector and a base, a lamp in circuit with the base of the first transistor and ground, a resistor in circuit with the base of the second transistor and ground, circuit means to direct a positive potential to the emitter of each transistor, resistance means connected in the potential directing circuit means of each transistor to positively bias each transistor, control means connected in the lamp circuit to the base of the first transistor between the lamp and the base and between the resistor and the base of the second transistor to determine the cutoif period of each transistor, means cross-connecting the collector of the second transistor to the lamp circuit of the first transistor at a point between the lamp and the control means, and means cross-connecting the, collectorcof the first transistor to the resistor circuit of the second transistor at a point between the resistor and the control means, the said lamp being energized or de-energiged in accord with the operating conditionofthesecondtransis fr, 7. A free running static flasher system comprising: pair of transistors, each including an emitter, a collector and a base, a lamp in circuit with the base of each transistor and ground, circuit means to apply a positive p01 tential to the emitter of each transistor, a resistor-condenser parallel circuit control means series connected in the lamp circuit to the base of each transistor between the lamp and the base to determine the cutoff perioldjo'lf each transistor, and means cross-.connectingthe collector of each transistor to the lamp circuit of the other 'tra'nsistor at a point between the lamp: 'andthe resistor-comdenser'control means, each said lamp being'energi'zed or' deenergized in accord with the operating condition of the transistor to which itis cross-connected.

8. The invention according to claim 7 'wherein resistance mansis'included in the potential applying cii -Q cuit means for each transistor to positively bias each transistor to therebycondition each transistor to act as a trigger means.

References Cited in the file of this patent a V ,UNITED STATES PATENTS 2,665,845

7 Trent Jan. 12, 1954 2,698,386 Eberhord et al. 2 Dec. 28, '1954' 2,707,752 Gabler May 3, 1955 2,737,587 Trousdal Mar. 6;1956' 2,747,111 Koch May 22, 1956 2,772,410 I Logue et al. Nov. 27, 1956 2,776,420';--2'Woll Ian. 1, 1957 2,806,153 Walker Sept. 10, 1957 2,827,568 Altschul Mar. 18, 1 958 2,829,257 Root Apr. 1,1958 2,831,127 Braicks' Apr.' 15, 1958 

